1. Sensation & Perception Chapter 5

2. Sensing & Perceiving Information
Sensation: Receiving
Perception: Organizing & Interpreting

3. Vision – The Eye Retina Light enters eye through the cornea
Passes through the pupil and lens
Focused into an image on the retina
Retina
Light sensitive inner surface of the eye
Contains Rods & Cones
Receptor cells convert light to neural impulses and send to brain
Brain reassembles impulses into an image

4. Vision – The Eye

5. Vision – Retina Receptors
Rods
detect black, white, and gray
necessary for peripheral and twilight vision
Cones
concentrated near the center of retina
function in daylight or well-lit conditions
detect fine detail
color vision

6. Vision--Receptors Receptors in the Human Eye Cones Rods Number
Location in
retina
Sensitivity in
dim light
Color sensitive?
Yes
Low
Center
6 million No
High
Periphery
120 million

7. The Eye
Optic Nerve: nerve that carries neural impulses from the eye to the brain
Blind Spot: point at which the optic nerve leaves the eye
No receptor cells
creates a “blind spot”

9. Vision – Feature Detection
Feature Detectors
nerve cells that respond to specific features of a stimulus
shape, angle, or movement
fMRI can be used to determine what object a person is looking at

10. Visual Information Processing
Parallel Processing
processing many parts of a problem all at once
the brain’s natural mode of information processing for many functions (including vision)

11. Visual Information Processing
Scene
Retinal processing:
Receptor rods and
conesbipolar cells
 ganglion cells
Feature detection:
Brain’s detector cells
respond to elementary
features-bars, edges, or
gradients of light
Abstraction:
Brain’s higher-level cells
respond to combined
information from
feature-detector cells
Recognition:
Brain matches the
constructed image with
stored images

12. Color-Deficient Vision
People who suffer red-green blindness have trouble perceiving the number within the design

13. Color Vision Young-Helmholtz trichromatic (three-color) theory
retina has 3 different color receptors (red, green, blue)
different combinations allow for the perception of any color
Opponent-process theory
opposing processes of retina enable color vision
e.g., some neurons are turned on by red and off by green

14. Audition Audition- the sense of hearing
Frequency- the number of complete wavelengths that pass a point in a given time
Pitch- a tone’s highness or lowness
depends on frequency
long sound waves = low frequency & low pitch
short sound waves = high frequency & high pitch

15. Audition--The Ear Sound waves Middle Ear
auditory canal eardrum (vibrates with the waves) middle ear cochlea (in inner ear)  triggers neural impulses (auditory nerve)  thalamus  auditory cortex (temporal lobe)
Middle Ear
chamber between the eardrum and cochlea
contains 3 tiny bones (hammer, anvil, stirrup) that transmit vibrations to the cochlea

16. Audition--The Ear Inner Ear innermost part of ear Contains the Cochlea
a fluid-filled tube through which sound waves trigger nerve impulses

18. Decibel Levels - Common Sounds

19. Locating Sounds sound reaches one ear more intensely and more quickly
auditory system is able to detect tiny differences
hearing loss in one ear = difficulty locating sounds

20. Touch Skin Sensations pressure warmth cold pain
only skin sensation with identifiable receptors
warmth
cold
pain
Rubber hand illusion

21. Pain Gate-Control Theory (1960s)
No theory explains all available findings
Gate-Control Theory (1960s)
provides a useful model for understanding pain
the spinal cord contains small fibers (conduct pain signals) and large fibers (conduct other sensory signals)
“gate” opened by the activity of pain signals traveling up small nerve fibers
“gate” closed by activity in larger fibers or by information coming from the brain

22. Pain Control Massaging area next to pain Distraction
Diverting the brain’s attention may bring relief
Pleasant imagery
Count backward
Virtual reality

23. Taste
Taste Sensations
sweet
sour
salty
bitter
savory (umami)

24. Taste Taste receptors Sensory Interaction
reproduce themselves every 2 weeks
taste sensitivity and # of taste buds decrease as we age
Sensory Interaction
one sense may influence another sense
the smell of food influences its taste
smell + texture = flavor
rubber hand illusion (vision & touch interact)

25. Smell humans can detect 10,000 odors olfactory receptor cells
respond to aromas
messages sent through receptor axons to the olfactory bulb in the brain
messages then travel from olfactory bulb to temporal lobe & limbic system
odors can evoke memories

26. Smell

27. Body Position and Movement
Sixth sense
Kinesthesis
the system for sensing the position and movement of individual body parts
interacts with vision
Vestibular sense
monitors head and body position to maintain balance
fluid in the inner ear moves when head moves
messages are sent to the cerebellum

28. Perceptual Organization - organizing & interpreting info from senses
Gestalt
an organized whole
tendency to integrate pieces of information into meaningful wholes
Necker cube

29. Perceptual Organization
First: Need to discriminate objects from backgrounds
Figure and Ground perceiving an object (figure) as distinct from its surroundings (ground)
In a busy restaurant:
voice you attend to = figure
all other voices = ground

30. Perceptual Organization- Gestalt
Next step: Need to organize the figure into a meaningful form
Grouping
the tendency to organize stimuli into meaningful groups
grouping rules identified by Gestalt psychologists
the “whole” that we perceive differs from the sum of its parts

31. Perceptual Organization- Gestalt
Grouping Rules
proximity - we group nearby figures together
similarity - we group similar figures together
continuity – we perceive continuous patterns
closure – we fill in gaps to create complete objects
connectedness - spots, lines, and areas are seen as a unit when connected

32. Perceptual Organization- Gestalt
Proximity
Similarity
Continuity
Closure
Connectedness
We see not six separate lines, but three sets of two lines. We see the triangles and circles as vertical columns of similar shapes, not as horizontal rows of dissimilar shapes. Continuity – this pattern could be a series of alternating semicircles, but we perceive it as two continuous lines – one wavy, one straight. We can perceive a triangle even when it is not complete. Connectedness: We perceive the two dots and the line between them as a single unit.

33. Perceptual Organization-Depth Perception
Visual Cliff

34. Perceptual Organization
Depth Perception
seeing objects in three dimensions
allows us to estimate distance
Visual Cliff
laboratory technique used to test depth perception

35. Perceptual Organization Depth Perception
Binocular cues –
depth cues
depend on use of two eyes
retinal disparity
images from the two eyes differ
brain compares the images to compute distance
the larger the difference, the closer the object

36. Perceptual Organization Depth Perception
Monocular Cues
depth cues needed for objects at further distances
available to each eye separately
relative height
higher objects seen as more distant
relative size
smaller image is more distant

37. Depth Perception Monocular Cues (continued) interposition
if one object blocks our view of another, we perceive that object to be closer

38. Depth Perception Monocular Cues (continued) relative clarity
hazy object seen as more distant
relative motion
as we move, stable objects appear to also move
fix gaze on object: those beyond appear to move with you; those in front appear to move backward
relative brightness
dimmer objects seem farther away

39. Depth Perception Monocular Cues (continued) linear perspective
parallel lines appear to converge with distance

40. Perceptual Constancy
perceiving objects as unchanging despite changes in illumination and retinal image
able to recognize objects despite changes in color, shape, & size

41. Shape Constancy
Shape constancy – as a door opens the shape projected on retina looks more like a trapezoid…but we still perceive it as rectangular.

42. Perceptual Constancy Color depends on context Color Constancy
we perceive familiar objects as having consistent color
even if illumination changes and alters the wavelengths reflected by the object

43. Perceptual Organization Size-Distance Relationship
Monsters are same size – but linear perspective tells brain that the monster in pursuit is farther away (and we therefore perceive it as larger). Ponzo illusion – same principle as monsters – two red bars are identical, but experience tells us that a more distant object can create the same-sized image as a nearer one only if it is actually larger. Therefore, we perceive the bar that seems farther away as larger.

44. Perceptual Organization- Size-Distance Relationship

45. Depth Perception

46. Perceptual Organization Müller-Lyer Illusion
The two red arrows are of equal length. The arrow configuration “angles in” (near the ticket counter) is always the front side of an object, the “angles out” configuration occurs at the far end of a room, for instance (here next to the door). So, given no further information, the brain assumes the “angles in” configuration to be closer, computes size constancy on it, and - given identical retinal size of the two angle arrangements – concludes that the “angle in”-line is shorter.

47. Perceptual Organization Brightness Contrast
Gray bars are the same color. The one on right appears brighter because of differences in the surrounding context.

48. Perceptual Interpretation
Perceptual Adaptation
(vision) ability to adjust to an artificially displaced visual field
glasses that invert view of the world (looks upside down)
humans can adapt relatively quickly and learn to coordinate movements accurately

49. Perceptual Interpretation
Perceptual Set
a mental predisposition to perceive one thing and not another
our experiences and expectations influence what we perceive

50. Perceptual Set – context effect
Pursuing monster may look more aggressive. Identical pursued monster may seem frightened.

51. Is There Extrasensory Perception?
Parapsychology
the study of paranormal phenomena
Astrological predictions
Psychic healing
ESP
Psychokinesis (“mind over matter”; levitating)

52. Is There ESP? Extrasensory Perception (ESP)
controversial claim that perception can occur apart from sensory input
types of ESP:
Telepathy (mind-to-mind communication)
Clairvoyance (sensing remote events)
Precognition (perceiving future events)